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LM74930-Q1: power input jump from 14volts to 19volts, output drop off and reboot in 1sec.

wang nick
Prodigy 80 points
Part Number: LM74930-Q1
Other Parts Discussed in Thread: LM74930,

Tool/software:

Hi  Texas team members:

     ISSUE: We has a project using LM74930-Q1,  in voltage jump test from 14volts to 19volts, we find that HGATE tend to low, FLT goes to low, output voltage dropped off.  And the in 1 second, the IC LM74930 return to normal automatically. 

Design: see the schematic drawing as above. 

Analysis: I guess it is caused by over voltage, so I removed R12814 and R 12817. no any change for the issue. Then I short the R ILIM to GND for over current concern, but there is no change. 

Question: what's the cause for the fault?

  • 0
    TI__Guru 50725 points

    Hi Wang,

    If the device is recovering after 1s, this means the device is entering some fault which triggers auto-retry mode. 68nF capacitor on TMR pin decides the 1second auto retry time.

    Since ILIM is not helping, there is a chance that SCP is triggering. You can increase the SCP resistor from 50ohms to higher to increase the threshold and verify.

    Probing current in the waveform can help in the debug.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Prodigy 80 points

    awesome, thanks for your excellent advice.